The invention refers to a remote object examination device provided with an image-recording system at the location of the object to be examined, an observation station spatially removed from it for evaluating the image and for the remote control of the image-recording system as well as with an intervening narrow-band telecommunications link, over which is transferred the image-data generated by the image-recording system to the observation-station using image data compression and/or reduction, as well as the control command signals generated from the observation station for the remote control of the image-recording system.
Such remote object examination devices are known in form of telemicroscopy systems for example, particularly as applied to telepathology. The object to be examined in this case is a tissue section prepared, for example, during an operation. The image-recording system comprises a microscope remote-controllable in all functions, an image-recording device for the microscope field, a transmitter for the image signal and a receiver for the control commands at the microscope. Transmitter and receiver as well as an additional speech channel are connected over an interface with a telecommunications link. The observation-station comprises a receiver, a monitor for the images to be returned, an appliance for the production of the control commands for the microscope and a transmitter for these control commands. The observer or expert, for example, a suitable computer or a pathologist, can appraise the transmitted microscope image. Transmitter and receiver as well as a speech channel are in turn connected by way of a suitable interface with the same telecommunications link as the image-recording system.
If the telecommunications link has a sufficient width for the transfer of a television signal, the observer at the observation station can use all functions of the spatially removed microscope just as if this were at his workplace. Such a telepathology system with wide band data transfer is described in U.S. Pat. No. 5,216,596. However, wide band telecommunication channels are comparatively costly for television signals and of only limited availability. It has already been proposed therefore, to operate telemicroscopy over the widely available and inexpensive, narrow-band channels of the telephone network. An installation with such narrow band technology employing the ISDN-Network is described by M. Oberholzer et al. In the paper xe2x80x9cTelepathology: frozen section diagnosis at a distancexe2x80x9d (1995), 426, page 3. However, the limited channel capacity forms a bottleneck for the transfer of the image data so that the on-line-impression for the user can be lost and instead of a moving image he will only receive a slow consecutive string of individual images. The result will be that the user will also lose the immediate impression of the effect of his microscope control commands, since for him their effect will be seen only after a substantial delay and in an altered context. The application of the technologies of video-telephony only allows the transmission with a quality of image which is inadequate for most of the applications considered here, such as telemicroscopy, teleendoscopy and telesonography.
Some measures have also already been proposed for the economic application of ISDN channels for narrow band telemicroscopy systems, such as, for example, the use of a particular auto-focus system and the application of a fixed, pre-determined, compression and reduction adapted to the particular system of the image data to be transferred, during their encoding, (see the papers by P. Schwarzmann, Telemikroskopie, Zentralbl. Pathol, 138, (1992) 6, page 383 and P. Schwarzmann et al., Telemicroscopy Stations for Telepathology Based on Broadband and ISDN Connections, 1995. 43, No. 4, page 209.
In an information bulletin published jointly by the Institute for Physical Electronics of the University of Stuttgart and German Telekom AG in 1995 on the scenario for the use of telepathology in rapid section diagnosis it is proposed to use the limited capacity of the existing ISDN-Network with the narrow-band telemicroscopy, but in an optimised form, where the system, dependent on the behavior of the user, i.e. the observer at the observation station, employs different strategies for image data-compression and reduction, for example, selection of a greater data-reduction in respect of color, local resolution and quantisation of the image data when a large number of image transfers are required per unit of time by reason of more rapid translation of the object under the microscope.
The technical problem which the invention seeks to solve is the preparation of an image transmitting remote object examination device of the type mentioned in the preamble, which is capable of automatically adapting itself in its transfer behavior very flexibly and variably to the appropriate situation, in such a way as to make optimal use of the existing narrow band data-carrying capacity.
The invention solves this problem by providing an image-transferring remote object examination device with the claimed features. This equipment comprises a system status determining unit which continuously records the entire image transfer-relevant system status including the system resources available in each case and as a function thereof automatically controls the image data compression and/or image data reduction process and/or the number of channels of a transmission path to be used in a transmission packet so that as well as the desired image-quality for a particular situation the best possible on-line image impression for the corresponding situation is also obtained in each case. In this way the device can be matched flexibly and variably in respect of image-transfer to the existing system status in each case.
This system status relevant to image-transfer and monitored by the system status-determining unit includes, depending on the system design, not only the user-behaviour, i.e. the control commands for the image-recording system entered by the observer, but also in particular the nominal condition in respect of the number individual channels of the telecommunication channel packet which are switched on, the type of telecommunication network to be used, the status of the coding unit carrying out image data compression and/or reduction, the type of image-recording equipment used and the current content of the image.
In this way, despite narrow-band telecommunication connection between the image-recording system and the observation position, the equipment in accordance with the invention is capable of maintaining for the user the impression of an on-line or real-time operation, with high image-quality. It is suitable for different types of remote object examinations, for example, remote material testing, telemicroscopy, teleendoscopy and telesonography, depending on the object examined and image-recording system employed.
With application of the equipment as a telemicroscopy system in telepathology, the pathologist is given a tool with which he can carry out telepathology with a high degree of telepresence.
In a further embodiment the parameters for the image data compression and/or reduction are among other things set as a function of the image content and the chosen image enlargement. Thus, for example, little structured, highly magnified images can, if necessary, be transferred at higher image transfer rates and lower resolutions than highly structured images of lower magnification.
A further embodiment uses as transmission path a telecommunication channel packet, where the number of channels currently used is set in accordance with the recorded system status and where the channel run times are automatically compensated for. The latter is of significance therefore, because the user himself in general has no control over the ways in which the individual communication channels, for example telephone channels, are switched. The ISDN Network technology has proved to be particularly suitable for such a packet solution.
In a further embodiment the image-recording system has auto-focus equipment available to it, the function of which is controlled as a function of the system status through a plurality of control parameters. By this means it is possible to avoid the transfer of the usually considerable quantity of image data required for image focusing alone. The control of the auto-focus equipment can be effected interactively or alternatively automatically from the system.
A further embodiment comprises an automatic brightness control on the side of the image-recording system which is optionally interactively or alternatively automatically operable. By means of such a brightness control also the transfer of image data which is redundant for image evaluation can be avoided so that he on-line impression of the images transmitted can be increased.
A further embodiment enables an impression of movement of transmitted, moving images inasmuch as the individual images, which are transferred in coarse steps which still partially overlap, and generate subsequently interpolated intervening images in the observation station and are successively brought to the display.
In a further embodiment an impression of movement of transmitted, moving images is conveyed, by not transferring the entire individual image in consecutive steps in each case during such an image movement but only the image areas which are new when compared with the preceding individual image. These image areas are then joined in the observation station to the previous individual image to produce the new individual image.
In a further embodiment the activity state of the same, i.e. of the transmission path utilization and system activity, is shown optically, acoustically and/or mechanically by means of power reaction on an associated operating control.
A further embodiment comprises, as operating control for tile observer at the observation station, a phantom, i.e. a copy, of the image-recording equipment used in the image-recording system, so that activities of the observer on the phantom are recorded and are converted into control commands for the corresponding adjustment of the real image-recording equipment.
A further embodiment is the possibility of the prophylactic transfer of image scenes, which are forecast to be required by the system at a later time, at periods with unused transfer channel capacity. For this, the equipment contains a predictor for the likely continuation of the remote examination of the object, which, for example, closes up the locations of object areas transmitted up to now to the places of the next image transfers, for example, through corresponding continuation of the path of the last transmitted areas.
In a further embodiment a representation tool may be provided for reproducing the image at the observation station, with which an overall image can be represented or a separate screen or in the form of a window inserted on the screen used for the detail images, where a marking surface of variable size defines the position of the current visual field of the image-recording equipment. If necessary, positions of the marking surface already used could remain marked on the overall image, in order to avoid duplicate examinations.
A further embodiment offers the option of the archiving selected images.
A further embodiment provides the ability to find again a certain desired image quickly and display it on the basis of the previously stored archiving data by corresponding control of the image acquisition system. This is useful, for example, if a preliminary examination first takes place and only subsequently is a definitive evaluation to be carried out on the basis of selected images. Here, it can be envisaged that the observer moves with the marking-surface to a certain area in the overall image, that is then represented at greater magnification, so that the equipment fulfills for the user a convenient magnifying glass function.
A further embodiment provides the possibility of transferring small, selectable image areas of an overall image in real time at maximum image quality, for which the capacity of the narrow band transmission path is generally adequate.